Heartthrob Dominic Cooper is left bemused when fellow chat show guest Miriam Margolyes admits she has no idea who he is - then says she does not like one of his most famous films.

The pair appear together as guests on The Graham Norton Show tonight but the veteran actress claims to be clueless about him.

She eventually recalls: "I think I've seen you in The History Boys - I think I saw that but I can't remember you."

Presenter Norton points out the the 35-year-old had a prominent role in box office hit Mamma Mia!, but she responds: "That was a dreadful film."

Margolyes - known to many for her role as Professor Sprout in the Harry Potter films - was equally unfamiliar with Lily Allen, who was also appearing on the programme.

"I'm 72 and I don't know about songs and singing, but I know you're highly admired," she told Allen.

Margolyes left many open-mouthed on a previous Norton appearance when she told The Voice coach Will.i.am she was "fascinated" by him, adding: " Unfortunately, I don't know many black people. We don't get to meet across the colour line much, except in showbusiness."

During the filming of tonight's programme Cooper - soon to be seen as author Ian Fleming in a Sky dramatisation of his life - also recalls an embarrassing wardrobe malfunction.

He told Norton how he was working as a waiter and had his hands full when he burst out of the front of his tight trousers, much to his embarrassment - and the horror of diners.

"I was working in a cafe wearing really tight jeans. I had two cappuccinos in one hand and pastries in the other and as I approached the table it fell out of my jeans and rested neatly on the table," he said.

"There was nothing I could do. The customers were repulsed and I just backed off."